The complex numbers Z and W are given by Z=3+3i and W=6-i. Giving your answers in the form of x+yi and showing how you clearly obtain them, find: i) 3Z-4W ii) Z*/W

i) 3Z-4WFor this question it is just the matter of substituting the complex numbers of Z and W into the equation. So, 3(4+3i)-4(6-i). Then multiply out the brackets to get 12+9i-24+4i. Finally simply to get -12+13i.This question is worth two marks and you get awarded one mark for the real part and one mark for the imaginary part.ii)Z*/WIn this question we are asked to divide the complex conjugate of Z by W. Z* = 4-3i, so Z*/W = *4-3i)/(6-i).To solve this we must make the denominator real. This is similar to rationalizing surds, the trick here is to multiply by the conjugate, so we get ((4-3i)x(6+i))/((6-i)(6+i))No we carefully multiply out to get (24+4i-18i-3i^2)/(36-i^2). The important part of multiplying by the complex conjugate is so that the complex part of the denominator cancels. Now we simply to get (27-14i)/37 remembering that i^2=-1Finally the last step is to write the answer in the form of x+yi to ensure we get full marks which is simply (27/37)-(14/37)iThis question was worth 4 marks. You get one mark for writing down the conjugate of Z correctly, you got a method mark for multiplying by the conjugate of W and then two accuracy marks for finding the real and imaginary parts.

JB
Answered by James B. Maths tutor

7063 Views

See similar Maths A Level tutors

Related Maths A Level answers

All answers ▸

The equation kx^2+4kx+5=0, where a is a constant, has no real roots. Find the range of possible values of k.


What is differentiation used for in the real world?


Evaluate the integral (write on whiteboard, too complicated to write here)


Integrate ⌠( xcos^2(x))dx


We're here to help

contact us iconContact ustelephone icon+44 (0) 203 773 6020
Facebook logoInstagram logoLinkedIn logo

MyTutor is part of the IXL family of brands:

© 2026 by IXL Learning